Splitting ARIN assignment

Ben Butler ben.butler at c2internet.net
Thu May 22 12:02:49 CDT 2008


I do appreciate real life is often more complex than high flying ideals.
But aggregation and general good practice would mean in an ideal world
you would invest in the internal infrastructure to connect your data
centres together with a network and run an IGP+iBGP plus advertise the
/21 eBGP at both sites to upstreams.  It could be argued that the cost
of building the network to run your AS is part and parcel of the expense
of opening new datacenter - rather than this ever increasing route table

Plus if you de-aggregate as intended you can not announce a covering
route for the /21 due to no internal connectivity and if this puts the
/22 under the minimum allocation size for the RIR block your IP space
comes from then don't be surprised when it gets filtered out and people
end up having to accept no routing to your network at all or, sum
optimal via a default.

But life is rarely as simple as ideals.

My 2e


-----Original Message-----
From: Scott Morris [mailto:swm at emanon.com] 
Sent: 22 May 2008 17:49
To: 'James Kelty'; nanog at nanog.org
Subject: RE: Splitting ARIN assignment 

As long as your upstreams/partners are cool with that, there is no
related designation between how addresses are allocated versus how they
are announced.

In other words, TECHNICALLY you could advertise a whole bunch of
You just run the risk of being filtered and/or ridiculed along the way.

But splitting the /22's from the same announcing AS shouldn't cause any
problems as long as you design your connectivity ok.


-----Original Message-----
From: James Kelty [mailto:jkelty at pandora.com]
Sent: Thursday, May 22, 2008 12:39 PM
To: nanog at nanog.org
Subject: Splitting ARIN assignment 

Hey all,

I'm looking for an opinion from the group. I have an ARIN /21 assignment
and a new requirement for a second data center. Rather than ask for
another assignment, I would like to advertise one /22 from one location
and the other /22 from the second location both with the same asn. My
apps will work that way, so I don't have an issue internally, but I'm
looking for a broader base opinion on that.

Thanks a lot!


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